A typical low silhouette panoramic dental X-ray machine is characterized by a vertical column which is supported by and rotatably mounted to a base structure, the column carrying, at its upper portion, the tubehead and camera assembly which rotates as a unit with the column about the patient's head. A rigid curved arm interconnects the tubehead and camera while maintaining a space therebetween for positioning of the patient's head. The tubehead and camera orbit the patient's head for a limited number of degrees of rotation in order to accomplish the panoramic radiographing or scan of the dental arch structure which scan consumes about 22 seconds. After the scan, the patient cannot readily exit the machine because of the presence of the rigid arm immediately to the fore. Thus, the column must be returned to its original starting position which also consumes about 22 seconds. The camera however yet blocks the convenient exit of the patient and thus the tubehead-camera assembly must be elevated, consuming approximately 11 more seconds for about 11 inches of travel. Thus, the total period of time consumed in radiographing one patient comprised a minimum of about 55 seconds.
It is significant to realize that even if the machine were designed to take radiographs in both rotational directions, which characterizes most current panoramic machines, a minimum of 33 seconds would be required for each patient, i.e., 22 seconds for the panoramic scan; and 11 seconds for the elevation of the tubehead-camera assembly to facilitate the patient's exit, as well as the entrance of the waiting patient.
Where radiographs are taken in both directions of rotation however, a significant tendency for unwanted variations in the radiographs frequently occur due to imperfect leveling of the machine. Other variations as well as non-reproducible radiographs result from a lack of synchronization among the different motors controlling film drive, chair shift, and camera position, when these motors are operated in both directions. These deficiencies are particularly important in the continuous mode of panoramically radiographing the centrals region where a very critical relationship exists among such variables.
Thus, it is preferable to radiograph in one direction of rotation only. However, in busy hospital clinics, Army hospitals, and the like, where patients are oftentimes waiting to be radiographed, and clinicians are anxious to cooperate, it is most desirable if the patient handling rate could be improved.
The present invention provides improved processes, and structures in support thereof, for expediting patient handling rate when panoramically radiographing dental patients in one direction only by means of low silhouette, or low center of gravity X-ray apparatus.
To more fully understand and appreciate the significance of the invention, reference is made to U.S. Pat. Nos. 2,798,958; 3,045,118; and 3,636,349, which disclose various types of structures, apparatus and mechanisms for orbiting tubehead-camera assemblies in circular or arcuate paths; for varying film travel speed in accordance with tubehead-camera assembly movements; for shifting the patient in a chair; and for providing continuous or discontinuous type radiographic images.